Method and apparatus for enhancing RLC for flexible RLC PDU size

ABSTRACT

Enhancements are provided for the radio link control (RLC) protocol in wireless communication systems where variable RLC packet data unit (PDU) size is allowed. When flexible RLC PDU sizes are configured by upper layers, radio network controller (RNC)/Node B flow control, RLC flow control, status reporting and polling mechanisms are configured to use byte count based metrics in order to prevent possible buffer underflows in the Node B and buffer overflows in the RNC. The enhancements proposed herein for the RLC apply to both uplink and downlink communications.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application Nos.60/887,831, filed Feb. 2, 2007, 60/895,471, filed Mar. 18, 2007, and60/913,728, filed Apr. 24, 2007, which are incorporated by reference asif fully set forth.

FIELD OF INVENTION

This application is related to wireless communications.

BACKGROUND

High speed packet access evolution (HSPA+) herein refers to the ThirdGeneration Partnership Project (3GPP) radio-access technologyevolutionary enhancement of high speed downlink packet access (HSDPA)and high speed uplink packet access (HSUPA) standards used in UniversalMobile Telecommunications Systems (UMTS) wireless communicationssystems. Some of the improvements to HSDPA (3GPP UMTS Standard Release5) and HSUPA (3GPP UMTS Standard Release 6) proposed as part of HSPA+include higher data rates, higher system capacity and coverage, enhancedsupport for packet services, reduced latency, reduced operator costs,and backward compatibility with 3GPP legacy systems. Herein, 3GPP legacysystems generally refer to any one or more of the pre-existing 3GPPstandards from Release 6 and earlier. Achieving these improvementsinvolves the evolution of both the radio interface protocol and networkarchitecture.

The following list includes relevant abbreviations:

-   -   3GPP—Third Generation Partnership Project    -   AM—Acknowledged Mode    -   AMD—Acknowledged Mode Data    -   ARQ—Automatic Repeat Request    -   CN—Core Network    -   CP—Control Plane    -   CS—Circuit Switched    -   DL—Downlink    -   HARQ—Hybrid Automatic Repeat Request    -   HSDPA—High Speed Downlink Packet Access    -   HSUPA—High Speed Uplink Packet Access    -   IP—Internet Protocol    -   LCID—Logical Channel Identifier    -   LTE—Long Term Evolution    -   MAC—Medium Access Control    -   PDCP—Packet Data Convergence Protocol    -   PDU—Packet Data Unit    -   PHY—Physical    -   PS—Packet Switched    -   QoS—Quality of Service    -   RAN—Radio Access Network    -   RLC—Radio Link Control    -   RNC—Radio Network Controller    -   CRNC—Controlling RNC    -   SRNC—Serving RNC    -   RNS—Radio Network Subsystem    -   RoHC—Robust Header Compression    -   RRC—Radio Resource Control    -   RRM—Radio Resource Management    -   Rx—Reception/Receiving    -   SAP—Service Access Point    -   SDU—Service Data Unit    -   SN—Sequence Number    -   TB—Transport Block    -   TBS—Transport Block Set    -   TF—Transport Format    -   TFC—Transport Format Combination    -   TFRC—Transport Format Resource Combination    -   TM—Transparent Mode    -   TM—Transparent Mode Data    -   Tx—Transmission/Transmitting    -   UE—User Equipment    -   UL—Uplink    -   UM—Unacknowledged Mode    -   UMD—Unacknowledged Mode Data    -   UP—User Plane    -   UMTS—Universal Mobile Telecommunications System    -   UTRAN—Universal Terrestrial Radio Access Network    -   WTRU—Wireless Transmit/Receive Unit

The Layer 2 radio interface protocols include medium access control(MAC) and radio link control (RLC) protocols. Some of the functions ofthe MAC and RLC protocols are discussed hereinafter, however, otherfunctions that are not discussed are assumed to function as described in3GPP standards.

Some of the main functions of the MAC protocol are:

-   -   Channel mapping of MAC packet data units (PDUs) to physical        channels    -   Multiplexing of higher layer data into packet data units (PDUs)    -   Quality of Service (QoS) that takes into account data priority        for scheduling and rate control    -   Link adaptation for QoS and multiplexing    -   Hybrid automatic repeat request (HARQ) for control of fast        retransmissions for error correction

The MAC layer multiplexes higher layer data into MAC PDUs. The MAC PDUsthat are sent to the physical (PHY) layer are called transport blocks(TBs). A set of TBs, referred to as a transport block set (TBS), aresent every transport time interval (TTI) to the PHY layer with acorresponding Transport Format (TF) that describes the physical layerattributes for that TBS. If the TBS is derived from combining ormultiplexing data from more than one logical RLC channel, then acombination of TFs known as transport format combination (TFC) is used.As part of link adaptation, the MAC layer performs the TFC selectionbased on RLC logical channel priority, RLC buffer occupancy, physicalchannel conditions, and logical channel multiplexing. The reference toMAC TFC selection here is generic and may include, for example,transport format resource combination (TFRC) selection in the high speedMAC (MAC-hs) protocol in HSDPA.

The RLC protocol in Layer 2 has a big impact on the latency andthroughput of data. The RLC protocol in 3GPP legacy systems, includingRelease 6 and earlier, is physically located in the radio networkcontroller (RNC) node.

Some of the main functions of the transmitting (Tx) RLC protocol thatoccur in the Tx RLC entity are:

-   -   Macro-diversity to enable a UE to be connected simultaneously to        two or more cells and receive data (optional)    -   Segmentation of higher layer radio bearers    -   Concatenation of higher layer radio bearers    -   Error detection and recovery of PDUs received in error    -   HARQ Assisted ARQ for fast retransmissions of PDUs received in        error

Some of the main functions of the receiving (Rx) RLC protocol that occurin the Rx RLC entity are:

-   -   Duplicate PDU detection    -   In sequence PDU delivery    -   Error detection and recovery of PDUs received in error    -   HARQ Assisted ARQ for fast retransmission of PDUs received in        error    -   Reassembly of higher layer data from received PDUs

Three modes of operation for the RLC layer are acknowledged mode (AM),unacknowledged mode (UM) and transparent mode (TM). In AM operation,which includes the transmission of some higher layer user plane data,the RLC protocol is bi-directional, such that status and controlinformation is sent from Rx RLC entity to Tx RLC entity. In TM and UMoperation, which includes the transmission of some control plane radioresource control (RRC) signaling data, the RLC protocol isunidirectional, such that the Tx RLC entity and Rx RLC entity areindependent with no status and control information exchanged. Also, someof the functions such as HARQ assisted ARQ and error detection andrecovery are typically used only in AM operation.

The RLC PDU sizes are determined by the RRC layer based on the long termquality of service (QoS) requirements of the application data carried bythe RLC logical channels. According to 3GPP legacy systems, includingRelease 6 and earlier, the RLC layer is configured on a semi-staticbasis by the RRC layer with predetermined RLC PDU sizes. Thus, the RLCPDU size is fixed on a semi-static basis by upper layers and sequencenumbers (SNs) are assigned to the RLC PDUs. AM data RLC PDUs arenumbered by modulo integer sequence numbers (SNs) cycling through thefield 0 to 4095.

The RLC PDU types are DATA, CONTROL and STATUS. The DATA PDU is used totransfer user data, piggybacked STATUS information and the polling bitwhen RLC is operating in AM, where the polling bit is used to request astatus report from the receiver. The CONTROL PDU is used for RLC RESETand RESET acknowledgement (ACK) commands. The STATUS PDU is used toexchange status information between two RLC entities operating in AM andcan include super-fields (SUFIs) of different types including, forexample, the Window Size SUFI and the Move Receiving Window (MRW) SUFI.

A transmission window refers to the group of PDUs that are beingprocessed for transmission or are being transmitted currently.Similarly, the reception window generally refers to the group of PDUsbeing received or processed at the receiver. The transmission orreception window size typically refers to a number of PDUs that arebeing transmitted or received, respectively, by the system. Thetransmission and reception window sizes need to be managed using flowcontrol in order not to overload the system and incur undesirable packetloss rates. Generally speaking, once a PDU has been successfullyreceived at the receiver, a new PDU may be added to the transmissionand/or reception window.

An RLC transmission window is composed of a lower bound and an upperbound. The lower bound consists of the SN of the PDU with lowest SNtransmitted and the upper bound consists of the SN of the PDU with thehighest SN transmitted. The RLC is configured with a maximumtransmission window size, such that the maximum number of PDUstransmitted from the lower bound to the upper bound should not exceedthe maximum window size. The RLC reception window is similarlyconfigured. The lower bound of the RLC reception window is the SNfollowing that of the last in-sequence PDU received and the upper boundis the SN of the PDU with the highest sequence number received. Thereception window also has maximum window size, where the maximumexpected PDU SN is equal to the lower bound SN plus the maximumconfigured window size. The transmission and reception windows aremanaged using transmission and reception state variables, respectively,as described hereinafter.

Among the techniques for flow control are RNC/Node B flow control, RLCflow control and RLC status reporting. RNC/Node B flow control refers tothe procedures to minimize the downlink data buffered in the Node B.Typically, data destined for a UE flows from the Core Network (CN)through a source radio network controller (SRNC) and a Node B, and adrift radio network controller (DRNC) in a drift situation where the UEis handed off to a cell with a different radio network subsystem (RNS).The Node B grants allocation credits to the SRNC, and DRNC under drift,allowing the SRNC to send an equivalent number of PDUs to the Node B,such that the RNC can not send more PDUs until more credits are granted.RLC flow control refers to the managing of packet transfer, includingwindow size, between the Tx RLC entity and the Rx RLC entity. RLC statusreporting allows the receiver to report status information to thetransmitter when polled by the transmitter.

According to 3GPP standards, various RLC protocol parameters for flowcontrol are signaled by upper layers to the RLC layer, including thefollowing parameters:

-   -   Poll_Window    -   Configured_Tx_Window_Size    -   Configured_Rx_Window_Size

These parameters, described in further detail hereinafter, are used bythe RLC layer along with various RLC state variables for flow control inorder to configure transmission and reception window size. According to3GPP legacy systems, such RLC state variables depend on SNs. Forexample, the following RLC transmitter state variables are affected bySNs:

-   -   VT(S) is the send state variable containing the SN of the next        AM data PDU to be transmitted for the first time    -   VT(A) is the acknowledge state variable containing the SN        following the SN of the last in-sequence acknowledged AMD PDU,        and forms the lower edge of the transmission window    -   VT(MS) is the maximum send state variable containing the SN of        the first AM data PDU that can be rejected by the peer receiver    -   VT(WS) is the transmission window size state variable

All arithmetic operations on VT(S), VT(A), VT(MS), VR(R), VR(H) andVR(MR) depend on one or more SNs. The following RLC receiver statevariables are also affected by SNs:

-   -   VR(R) is the receive state variable containing the SN following        that of the last in-sequence AM data PDU received    -   VR(H) is the highest expected state variable containing the SN        following the highest SN of any received AM data PDU    -   VR(MR) is the maximum acceptable receive state variable        containing the SN of the first AM data PDU that shall be        rejected by the receiver

In 3GPP legacy systems, many functions needed to support data transferservice, such as RNC/NodeB flow control, RLC flow control and RLC statusreporting, are based on SNs or effectively the number of PDUs when theRLC PDU size is fixed. The reason is that transmitting and receivingwindow size can be accurately characterized using the number of PDUs andthe known and fixed PDU size. However, in proposals for HSPA+, the RLCmay be configured by the upper layers to allow flexible RLC PDU sizes.If upper layers such as the RRC layer configure a flexible RLC PDU sizeoperation then the RLC PDU size is variable up to a semi-staticallyspecified maximum RLC PDU payload size.

It is recognized herein that existing SN based RLC operations may notfunction efficiently with flexible RLC PDU size. The reason is thatusing the number of PDUs to define window size will result in variablewindow size causing possible buffer overflows in the RNC and bufferunderflows in the Node B. Accordingly, it would be beneficial to providealternate methods for configuring window size for flexible RLC PDU sizeoperations.

SUMMARY

Enhancements for radio link control (RLC) protocol for high speed packetaccess evolution (HSPA+) and other wireless systems, such as long termevolution (LTE) system, where variable RLC packet data unit (PDU) sizeis allowed are disclosed. When RLC PDU sizes are not fixed, radionetwork controller (RNC)/Node B flow control, RLC flow control, statusreporting and polling mechanisms do not only depend on sequence numbers(SNs) or number of PDUs, but are configured to use byte count abasedmethods. The proposed byte count based methods for the RLC apply to bothuplink and downlink communications.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example and to be understood in conjunction with theaccompanying drawings wherein:

FIG. 1 shows a structure of a super-field (SUFI) in an RLC STATUS packetdata unit (PDU);

FIG. 2 shows a flow diagram of a RNC/Node B flow control using abyte-based credit allocation in accordance with the teaching herein;

FIG. 3 shows a flow diagram of an RLC transmission (Tx) window update inaccordance with the teaching herein;

FIG. 4 shows a flow diagram of an RLC reception (Rx) window update inaccordance with the teaching herein; and

FIG. 5 shows a flow diagram for enhanced octet-based RLC PDU creation inaccordance with the teachings herein.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

Byte count based methods to enhance radio network controller(RNC)/Node-B flow control, radio link control (RLC) flow control, RLCstatus reporting and polling mechanisms for flexible RLC packet dataunit (PDU) size are provided herein. The proposed enhancements enableefficient operation of RLC functions when RLC PDU size is flexible,improving legacy RLC functions based on sequence numbers (SNs) that weredesigned for fixed RLC PDU size. The proposed RLC enhancements apply toboth uplink (UE to Universal Terrestrial Radio Access Network (UTRAN))and downlink (UTRAN to UE) communications, and may be used in anywireless communication system including, but not limited to, high speedpacket access evolution (HSPA+), long term evolution (LTE) and widebandcode division multiple access (WCDMA) systems. For wireless systems suchas LTE, UTRAN is equivalent to evolution UTRAN (E-UTRAN).

The proposed RLC enhancements may be used in architecture where the RLCoperates either fully in the Node B, or partially in the RNC andpartially in the Node-B. The proposed RLC enhancements are principallydescribed herein with reference to HSPA+. Many functions and parametersare based on functions and parameters for HSDPA and HSUPA and may beunderstood in conjunction with 3GPP technical specifications (TSs)including the 3GPP RLC Protocol Specification for Release 7 (see 3GPP TS25.322 V. 7.2.0) which is incorporated herein. It is assumed that theRLC can be configured by the higher layers to support flexible PDU sizewith a specified maximum RLC PDU payload size. It also assumed that themaximum RLC PDU size may be inferred from the specified maximum RLC PDUpayload size. Alternatively, the maximum RLC PDU size may be directlyspecified. Also, the terms bytes and octets are used interchangeably, aswell as terms transmitter and sender.

One or more of the following metrics may be used, alone or incombination, for defining and managing window size when flexible RLC PDUsize is configured by the RRC:

-   -   Number of bytes    -   Number of blocks where each block is a fixed number of bytes    -   Number of PDUs or sequence numbers (SNs)

The metric(s) used for window definition are signaled and negotiatedduring RRC setup, configuration and reconfiguration procedures for theradio bearer. The metric(s) for window size listed hereinbefore may beapplied in all messaging that updates the window for flow control duringa connection. For example, the window size metrics may be included inthe Window Size super-field (SUFI) and Move Receiving Window (MRW) SUFIin RLC CONTROL or STATUS PDUs.

In the case of acknowledged mode (AM) RLC, to support flexible RLC PDUsize in the RRC configuration and reconfiguration of RLC with radiobearer information elements (RLC Info), any one or more of the followinginformation may be provided by the RRC to the RLC to signal the use offlexible RLC PDU size:

-   -   CHOICE Downlink RLC mode information including a new indicator        for the flexible RLC PDU size mode in addition to the other RLC        modes. When flexible RLC PDU size mode is indicated, the RLC        entities may interpret the other RLC protocol parameters in        accordance with this mode.    -   Any other new information element as part of RLC Info may also        be used to indicate the flexible RLC PDU size mode.    -   Downlink (DL) RLC PDU size information in bits may be re-used        and interpreted in the context of flexible RLC PDU size mode as        follows:        -   as an RLC scale parameter in octets (after dividing the            number of bits by 8), sent specifically for scaling or            multiplying other protocol parameters specified in the            number of PDUs as described hereinafter, where the RLC Scale            parameter has the same value at the receiving (Rx) RLC            entity and transmitting (Tx) RLC entity, or        -   as specifying the maximum RLC PDU size in the flexible RLC            PDU size mode, where the maximum RLC PDU size may in turn            additionally be used as the RLC Scale parameter described            above.    -   Protocol parameters signaled by upper layers such as the RRC to        the RLC, including but not limited to Poll_PDU, Poll_SDU,        Configured_Tx_Window_Size, and Configured_Rx_Window_Size (see        3GPP TS 25.322 V. 7.1.0 Section 9.6), may be specified and        interpreted in the following two ways:        -   In number of PDUs, or service data units (SDUs) in the case            of Poll_SDU, which is an integer value from which the RLC            can derive the window size in octets by performing a            mathematical calculation. For example, the specified number            of PDUs (or SDUs in case of Poll_SDU) can be multiplied with            the RLC Scale parameter in octets as specified by upper            layers.        -   In units of bytes, where a new field may be defined for this            option to hold the protocol parameter in bytes.

In an RLC STATUS PDU, a Window Size Super Field (SUFI), used by thereceiver to configure the window size of the transmitter, is configuredto provide an octet quantity. This enhancement is used when flexible RLCPDU size mode is set by RRC as described above, and may be specified intwo ways:

-   -   In number of PDUs from which the RLC derives the equivalent        quantity in octets by performing a mathematical calculation. For        example, the specified number of PDUs may be multiplied with the        RLC scale parameter in octets specified by upper layers and        described above.    -   In units of bytes as a new SUFI with type, length and value        components. For example, a currently unused or reserved type        field of 4 bits in length, such as bits 1000 shown in Table 1,        may be used to introduce a new SUFI type for specifying the        number bytes, WINDOW_BYTES SUFI, as shown in Table 1 and FIG. 1,        where the SUFI length component is defined large enough to hold        the largest possible window size SUFI value in bytes.

TABLE 1 Definition of a new SUFI type 1000 for the WINDOW_BYTES SUFIadded to the existing SUFI type fields which are 4 bits long BitDescription 0000 No More Data (NO_MORE) 0001 Window Size (WINDOW) 0010Acknowledgement (ACK) 0011 List (LIST) 0100 Bitmap (BITMAP) 0101Relative List (Rlist) 0110 Move Receiving Window (MRW) 0111 MoveReceiving Window Acknowledgement (MRW_ACK) 1000 Window Size Bytes(WINDOW_BYTES) 1001- Reserved (PDUs with this encoding are invalid forthis version 1111 of the protocol)

RNC/Node B Flow Control

Enhancements to RNC/Node B flow control are described herein for thecase where the RLC entity is retained in the RNC. However, similarenhancements may be defined where the RLC entity is in the RNC and theNode B. According to existing 3GPP standards, as described in 3GPP TS25.425 for the UTRAN Iur interface user plane protocols for CommonTransport Channel data streams between an RNC and Node B, and 3GPP TS24.435 for the UTRAN Iub interface user plane protocols for CommonTransport Channel data streams between two RNCs, a data MAC (MAC-d)entity may be retained in the RNC to receive RLC PDUs and forward themto the high speed MAC (MAC-hs) entity in the NodeB after applyingappropriate header information. In 3GPP legacy systems, the Node B sendscapacity allocation frames to a serving RNC (SRNC), and possibly controlRNC (CRNC), indicating the maximum PDU size and number of PDUs that canbe sent. Additionally, parameters can be sent so that the allocation isperiodic for a fixed number of periods or for an indefinite period oftime.

The number of MAC PDUs sent from the RNC to the Node B and thecorresponding time interval for transmission is regulated by a flowcontrol algorithm, which is based upon a credit allocation scheme.Credits represent the number of MAC-d PDUs that may be transmitted. TheRNC requests credits and the Node B grants them along with a specifiedtime interval for transmission.

When the RLC PDU size is variable, the MAC-d PDU size is therefore alsovariable. Thus, it is insufficient to specify the number of credits interms of the number of MAC-d PDUs. There are multiple possibleapproaches to performing RNC/Node B flow control with a variable sizedMAC-d PDU. One possibility is to eliminate RNC/Node B flow control,however, this would require relying on user data protocols such astransport control protocol (TCP) to do the flow control for the network,and additionally handle the interaction between the TCP window and theRLC window.

Alternatively, the credit allocation can be specified in bytes insteadof in number of PDUs, which can be done in two ways. A new field may beadded to existing frames to specify the number of bytes of creditsinstead of the number of PDUs. Alternatively, an indication can besignaled at radio bearer setup or reconfiguration, or in each applicablecontrol frame using an existing control frame or a new control frame,which indicates that the allocation is actually a byte allocation bymultiplying the credit by the maximum PDU size in bytes producing a bytetotal. Accordingly, the maximum number of PDUs that can be transferredfrom the RNC to the Node B would not equal the signaled credit in termsof a number of PDUs, but would be limited by the total number of bytesin the PDUs. Using a byte-based approach, the RNC may optionallymaintain a mapping of the PDU SN to its length in bytes. Once the RNCreceives the credit allocation from the Node B, it is allowed totransmit as many PDUs as it can without violating the byte lengthconstraint specified by the new byte-length based credit allocation.

FIG. 2 shows a flow diagram of a RNC/Node B flow control using abyte-based credit allocation. A Node B signals a credit allocation inbytes (step 205). An RNC receives the credit allocation in bytes (step210). The RNC maintains a mapping of PDU SN to PDU length in bytes (step220), and transmits PDUs without exceeding the received creditallocation (step 220).

RLC Flow Control

RLC flow control is achieved by advancing the RLC Tx window when the PDUat the lower end of the utilized transmission (Tx) window is positivelyacknowledged, and thus received correctly, while still staying withinthe limits imposed by the maximum window size. The PDU at the lower endof the Tx window is defined as the PDU following the last in-sequencePDU acknowledged. For the case when flexible RLC PDU size is configured,appropriate steps should be taken so that the maximum window size limitis not violated. The Tx window size is specified in terms of bytes.

FIG. 3 shows a flow diagram for a method for updating an RLCtransmission (Tx) window 300. Following initialization and setup of theRLC, an RLC Tx operation is executed (step 305). An RLC Tx operation maybe, for example, the reception of status and control information formthe RLC receiver. The RLC Tx entity decides whether or not to remove oneor more PDUs from the utilized Tx window and increase the lower end theutilized Tx window (step 310). One or more PDUs may be removed if:

-   -   the PDU(s) were positively acknowledged by the receiver, or    -   the PDU(s) were negatively acknowledged by the receiver, but the        RLC transmitter decides to discard this PDU due to other reasons        such as the receiver exceeding the transmitter's maximum number        of retries, or    -   as a result of a timer based discard in the transmitter.

For ease of description, the following notation is used for certainquantities related to the RLC Tx entity:

-   -   TxWMAX: length in bytes of maximum window size    -   TxWUTIL: length in bytes of utilized Tx window, or        alternatively, the length in bytes of packets that are        acknowledged within the window bounded by state variables V(A)        and V(T)    -   TxL: length in bytes of the one or more PDUs that are discarded        due to RLC SDU discard procedure or due to reception of one or        more acknowledgements    -   TxN: length in bytes of the next one or more PDUs to be        transmitted for the first time

The RLC Tx entity computes the following window length (WL) quantity(step 315):WL=TxWUTIL−TxL+TxN.  Equation (1)

The RLC Tx entity determines if the WL quantity is less than the maximumwindow size TxWMAX (step 320). If WL is not less than TxWMAX, then thenext one or more PDUs are not transmitted and the upper end of thewindow is not increased (step 325). If WL is less than TxWMAX, then thenext one or more PDUs are transmitted and the upper end of the window isincreased (step 330).

A similar RLC flow control method is applied at the RLC Rx entity whenflexible RLC PDU size is configured, in order to ensure that the maximumwindow size limit is not violated. The Rx window size is specified interms of bytes. FIG. 4 shows a flow diagram of a method for updating anRLC reception (Rx) window 400 in accordance with the teachings herein.After initialization and setup of the RLC, an RLC Rx operation isexecuted (step 405). An RLC Rx operation may be, for example, thereception of a new PDU. The RLC Rx entity decides whether or not toincrease the lower end the Rx window (step 410). The RLC Rx entity mayincrease the lower end of its Rx window and thereby decrease RxWUTIL if:

-   -   it receives the PDU with SN following that of the last        in-sequence PDU received, or    -   it receives a Move Receiving Window (MRW) from RLC Tx entity.

For ease of description, the following notation is used for certainquantities related to the RLC Rx entity:

-   -   RxWMAX: length in bytes of maximum window size    -   RxWUTIL: length in bytes of utilized Rx window    -   RxD: length in bytes of one or more PDU(s) that are removed from        the receive window due to in-order reception    -   RxN: length in bytes of the next one or more PDU(s) to be        received for the first time

The RLC Rx entity computes the following window length (WL) quantity(step 415):WL=RxWUTIL+RxN−RxD.  Equation (2)The RLC Rx entity determines if the WL quantity is less than the maximumwindow size RxWMAX (step 420). If WL is not less than RxWMAX, then thenext PDU(s) are not received and the upper end of the Rx window is notincreased (step 425). If WL is less than RxWMAX, then the next PDU(s)are received, without discarding the PDU with a SN following that of thehighest received SN, and the upper end of the Rx window is increased(430).

The setting of the RLC transmitter and receiver state variables usingoctet-based methods is described hereinafter. When flexible RLC PDU sizemode is set by the RRC layer and the RLC operates in AM, AM data RLCPDUs are numbered by modulo integer sequence numbers (SN) cyclingthrough a field. Generally, this field ranges from 0 to 4095, although adifferent maximum value may be configured by the RRC or other upperlayers. Recall that arithmetic operations on VT(S), VT(A), VT(MS),VR(R), VR(H) and VR(MR) are affected by the SN modulus.

A parameter or state variable Maximum_Tx_Window_Size in octets may bemaintained by the RLC transmitter. This parameter is initially set equalto the protocol parameter Configured_Tx_Window_Size in octets sent bythe upper layers, and may be updated later to an octet quantityindicated by the Window Size SUFI in a RLC STATUS PDU. The statevariable VT(WS) may be derived from the Maximum_Tx_Window_Size inoctets, and may be set equal to the largest non-negative integer notgreater than 4095 (or a maximum value configured by RRC/upper layers),such that the octet length of the window bounded by VT(A) andVT(A)+VT(WS) does not exceed the Maximum_Tx_Window_Size in octets. Thestate variable VT(WS) is updated when the Maximum_Tx_Window_Size inoctets is updated. Alternatively, the state variable VT(WS) may bederived as the largest non-negative integer not greater than 4095 (or amaximum value configured by RRC/upper layers), such that the octetlength of the window bounded by VT(A) and VT(A)+VT(WS) does not exceed:

-   -   the protocol parameter Configured_Tx_Window_Size in octets, and    -   the Window Size SUFI referring to an octet quantity in a RLC        STATUS PDU as defined above.

The state variable VT(MS) is a SN calculated as VT(MS)=VT(A)+VT(WS)where VT(WS) is derived as described above. The state variable VR(MR) isa SN derived from the Configured_Rx_Window_Size in octets sent by upperlayers, such that the length in octets of the window bounded by VR(R)and VR(MR) is as large as possible but not exceeding theConfigured_Rx_Window_Size in octets.

Enhancement to RLC PDU Creation

FIG. 5 shows a flow diagram for a method for enhanced octet-based RLCPDU creation 500 for both uplink and downlink, based on the followingparameters:

-   -   Current_Credit: In the uplink, this is the amount of data that        can be transmitted based on MAC link adaptation and is sent by        the MAC to the RLC in the UE, or in the Node B in flat        architecture systems such as long term evolution (LTE) and        Release 8 wideband code division multiple access (WCDMA)        systems. In the downlink, this is the result of the remaining        credit allocation plus any new credit allocation sent from the        Node-B to RNC. This quantity is represented in octets.    -   Available_Data: This is the data available to be transmitted in        RLC entity. This quantity is represented in octets.    -   Leftover_Window: This is the length of the window bounded by        VT(S) and VT(MS) in the RLC transmitter. This quantity is        represented in octets.    -   Maximum_μLC_PDU_size: This the maximum RLC PDU size as        configured by the upper layers, for example, the RRC layer.    -   Minimum_μLC_PDU_size: This is a parameter configured by the        upper layers, for example, the RRC Layer, which specifies the        minimum RLC PDU size. Alternatively, the upper layers may        specify the minimum RLC PDU payload size from which the        Minimum_RLC_PDU_size may be inferred.

Upon initiation of RLC PDU generation, in each transmission timeinterval (TTI), the following quantities are calculated (step 505):X=Min{Current_Credit, Available_Data, Leftover_Window}  Equation (3)N=Floor{X/Maximum_RLC_PDU_size}  Equation (4)L=X mod Maximum_RLC_PDU_size  Equation (5)where the function Min{•} returns the minimum value from the set, thefunction Floor{•} returns the nearest lower integer value, and a mod bis the modulo b division of a. N RLC PDUs of size Maximum_RLC_PDU_sizeare generated (step 505). Optionally, if L is different than zero, oneadditional RLC PDU may be created for the TTI. It is determined if X isequal to the Leftover_Window or Current_Credit parameters (step 510). Ifso, it is determined if L is greater than the Minimum_RLC_PDU_sizeparameter or if X is equal to the Available_Data (515). If L is greaterthan the Minimum_RLC_PDU_size, or if X is equal to the Available_Data,then an RLC PDU of length L is generated (520). Also, if X is not equalto Leftover_Window or Current_Credit, then an RLC PDU of length L isgenerated (520). Optionally, if L is less than Minimum_RLC_PDU_size, anRLC PDU of Minimum_RLC_PDU_size may be created. The generated RLC PDU(s)are stored in a buffer for transmission (525). The method 500 may berepeated every TTI, or alternatively when data is available or requestedby lower layers (530).

As a result of method 500 described hereinbefore, the number of PDUs oflength equal to the maximum RLC PDU size generated in this period oftime, which is typically a TTI or some other system specified timeperiod, is equal to the greatest non-negative integer less thanMin{Current_Credit, Available_Data,Leftover_Window}/Maximum_RLC_PDU_size. If Min{Current_Credit,Available_Data, Leftover_Window}=Current_Credit, then another RLC PDUmay also be generated in the same period of a size equal toMin{Current_Credit, Leftover_Window, Available_Data} modMaximum_RLC_PDU_size. If Min{Current_Credit, Available_Data,Leftover_Window}=Available_Data, then another RLC PDU may also begenerated in the same period of size equal to Min{Current_Credit,Leftover_Window, Available_Data} mod Maximum_RLC_PDU_size. IfMin{Current_Credit, Available_Data, Leftover_Window}=Leftover_Window,then another RLC PDU may also be generated in the same period of sizeequal to Min{Current_Credit, Leftover_Window, Available_Data} modMaximum_RLC_PDU_size, if and only if this PDU's length is greater thanMinimum_RLC_PDU_size.

Variable size RLC PDU creation may also be applied without theMinimum_RLC_PDU_size and/or the Maximum_RLC_PDU_size limitations.Alternatively, it is also possible to define maximum and minimum RLC PDUsize limitations and to allow the transmitter to choose a size withthese limitations without requiring a TTI based relationship to MAClayer link adaptation. Alternatively, a RLC PDU of size X can be createdin a system where parameters minimum_RLC_PDU_size andmaximum_RLC_PDU_size are not defined.

As an alternative method for performing window management, the currentstate variables used for fixed RLC PDU size are maintained and can beused simultaneously with a set of new variables that deal with the bytecount of flexible RLC PDUs. More specifically, some of the valuesmaintained in terms of number of PDUs and processed as in thenon-enhanced RLC may include:

-   -   The RLC transmitter state variables: VT(S), VT(A), VT(MS),        VT(WS)    -   The RLC receiver state variables: VR(R), VR(H), VR(MR)

VT(WS) is maintained in terms of maximum number of PDUs and it isoriginally configured by higher layers based on theConfigured_Tx_Window_size parameter provided in number of PDUs. Thisvalue can correspond to the maximum number of PDUs allowed for thewindow, and/or the maximum number of PDUs limited by the number of bitsused for the sequence number. For example, if 12 bits are used then upto 2¹² or 4096 PDUs can be supported. Optionally, for flexible RLC PDUsize, the VT(WS) can be prohibited from being updated by the receiverusing the WINDOW SUFI. The calculation of VT(MS) preferably remains thesame, where VT(MS)=VT(A)+VT(WS). The other receiver state variables mayalso be maintained and processed according to 3GPP legacy standards.

In addition to these variables, the variables dealing with the bytecount for the transmitter and receiver are also maintained andprocessed. Some variables that can be used are listed below, and areassumed to be maintained in terms of bytes. The names of these variablesare used for description purposes but may be given any name. Thevariables include:

-   -   Configure_Tx_Window_size_bytes—This protocol parameter indicates        both the maximum allowed transmission window size in octets and        the value for the state variable VT(WS)_bytes. This variable can        be configured, for example, in any of the following ways: by        higher layers, by the network, preconfigured in the UE, or        determined by the UE based on memory requirements or UE        category.    -   VT(WS)_bytes—Transmission window size given in octets. This        state variable contains the size in octets that shall be used        for the transmission window. Optionally, VT(WS)_bytes shall be        equal to the WSN field when the transmitter receives a STATUS        PDU including a WINDOW_BYTE SUFI. The initial value and maximum        value for this state variable is given by Configure_Tx Window        size bytes.    -   Window_utilization: length in bytes of TX utilized window. For        every new transmission the byte count is incremented by the RLC        PDU size to be transmitted for the first time. For every PDU        discarded the byte count is decremented by the RCL PDU size to        be discarded.    -   RxWMAX: length in bytes of maximum Rx window size provided in        octets by higher layers.    -   RxWUTIL: length in bytes of Rx utilized window. The variable        will be incremented by received RLC PDU size upon reception of a        new RLC PDU, and it will be decremented by RLC PDU size when a        RLC PDU is removed from the buffer.    -   RxN: length in bytes of received PDU for the same time

The combination of the old and new state variables will allow the RLC tocontrol the Tx and Rx windows in terms of maximum amount of bytesallowed and also in terms of maximum number of PDUs allowed (limited bythe number of sequence numbers available for transmission).

RLC Procedure Affected by the Introduction of Flexible RLC PDU Size

Some of the procedures in 3GPP TS 25.322 V7.1.0 may be updated asdescribed by the teachings herein in order to support and manage Tx andRx windows for flexible RLC PDU include the following procedures:

-   -   Transmission of AMD PDU    -   Submission of AMD PDUs to lower layer    -   Reception of AMD PDU by the receiver    -   Reception of AMD PDU by the receiver    -   Receiving an AMD PDU outside the reception window

The procedures associated with reconfiguration and re-initialization ofthe Tx and Rx state variables can be updated.

Transmission of Acknowledge Mode Date (AMD) PDU

For fixed RLC PDU, when AMD PDUs are retransmitted, the transmitter hasto ensure that the SN of the AMD PDU is less than the maximum sendvariable VT(MS). The SN of retransmitted AMD PDU might be greater thanVT(MS) if the window size has been updated by the receiver using WINDOWSUFI.

For flexible RLC PDU size, the transmitter can also check that the Txwindow utilization up to the AMD PDU to be retransmitted does not exceedthe maximum window size in bytes using state variable VT(WS)_bytes. Thestate variable Window_utilization is the total size of transmitted RLCPDUs in the retransmission buffer. Therefore, when this condition ischecked the utilization up to the retransmitted SN has to be calculatedindependently. If Window_utilization is less than VT(WS)_bytes, then thecondition will be met automatically, however if window_utilization isgreater than VT(WS)_bytes, the buffer utilization up to the AMD PDU hasto be calculated in order to ensure that it will not exceedVT(WS)_bytes. So optionally, the buffer utilization is calculated if thewindow_utilization exceeds the state variable VT(WS)_bytes.

For example, the AMD PDU transmission procedure can be modified in thefollowing way to account for fixed and flexible RLC PDU sizes, assignaled by upper layers:

-   -   If fixed RLC PDU size is configured then:        -   for each AMD PDU which has been negatively acknowledged:            -   if the AMD PDU SN is less than VT(MS) then:            -   schedule the AMD PDU for retransmission;    -   If flexible RLC PDU size is configured then:        -   for each AMD PDU which has been negatively acknowledged:            -   if (1) the window utilization up to the AMD PDU SN is                less than VT(WS)_bytes, where this condition is always                true if window_utilization<VT(WS)_bytes, or is                calculated as the used window up to SN and (2)                optionally, if the AMD PDU SN is less than VT(M) then:            -   schedule the AMD PDU for retransmission.

Submission of AMD PDUs to Lower Layers

One of the conditions to allow the transmission of an AMD PDU is thatthe AMD PDU SN is less than the state variable VT(MS). When flexible RLCPDU size is configured, an additional condition to check that the windowutilization for the transmitted or retransmitted PDU does not exceedmaximum window size in bytes should also be verified. The lower layersinclude the MAC layer and physical layer.

According to one approach, if one or more AMD PDUs have been scheduledfor transmission or retransmission (see, for example, 3GPP TS 25.322V7.1.0 subclause 11.3.2), then the sender may:

-   -   not submit any AMD PDUs that it is not allowed to transmit to        lower layers. When fixed RLC PDU size is configured, an AMD PDUs        is allowed to be transmitted if the AMD PDU has a SN<VT(MS) or        if the AMD PDU has a SN equal to VT(S)-1. If flexible RLC PDU        size is configured, then the AMD PDU is allowed to be        transmitted if (1) it has a SN<VT(MS) or, optionally, the AMD        PDU has a SN equal to VT(S)-1, and (2) if the transmitted AMD        PDU will not cause the window utilization, determined by        window_utilization+AMD PDU size, to exceed VT(WS)_bytes.        Additionally, an AMD PDU is allowed to be transmitted if the AMD        PDU is not restricted to be transmitted by a local suspend        function (see, for example, 3GPP TS 25.322 V7.1.0 subclause).    -   inform the lower layers of both the number of AMD PDUs scheduled        for transmission or retransmission and allowed for transmission        or retransmission. Optionally, if flexible RLC PDU size is        configured, the sender can inform the lower layers of the number        of bytes to be scheduled.    -   set the AMD PDU contents according to, for example, 3GPP TS        25.322 V7.1.0 subclause 11.3.2.1.    -   submit to the lower layers the requested number of AMD PDUs.        Optionally, if flexible RLC PDU size is configured, the sender        may also submit to lower layers a number of bytes requested by        the lower layers.    -   treat retransmissions with higher priority than AMD PDUs        transmitted for the first time.    -   update the state variables for each AMD PDU submitted to lower        layer (see, for example, 3GPP TS 25.322 V7.1.0 subclause 9.4 for        the state variables) except VT(DAT), which counts the number of        times a AMD PDU has been scheduled to be transmitted and which        has already been updated when the AMD PDU contents are set (see,        for example, 3GPP TS 25.322 V7.1.0 subclause 11.3.2).    -   if flexible RLC PDU size is configured, then update the        window_utilization variable, therefore updating the variables        associated WITH keeping track of byte count.

if (1) the polling bit, used by the transmitter to request a statusreport from the receiver, is set to “1” in any of the AMD PDUs, and (2)Timer_Poll, a timer for tracking AMD PDU containing a poll as indicatedby lower layers, is configured, then start the timer Timer_Poll (see,for example, 3GPP TS 25.322 V7.1.0 subclause 9.5).

-   -   buffer the AMD PDUs that are not submitted to the lower layers        according to a discard configuration (see, for example, 3GPP TS        25.322 V7.1.0 subclause 9.7.3).

Reception of AMD PDU by the Receiver

The procedure associated with the reception of an AMD PDU by thereceiver is updated to include and update of the receiver statevariables associated with the byte count for flexible RLC PDU size. Theenhanced procedure is defined as follows. Upon reception of an AMD PDU,the receiver shall:

-   -   in the UE:        -   if the downlink AMD PDU size has not yet been set then            -   set the downlink AMD PDU size to the size of the                received PDU.    -   update receiver state variables VR(R), VR(H) and VR(MR) for each        received AMD PDU (see, for example, 3GPP TS 25.322 V7.1.0 clause        9.4);    -   if flexible RLC PDU size is configured then        -   update the RxWUTIL state variable by setting RxWUTIL equal            to the RxWUTIL plus the size of new received RLC PDUs minus            the size RLC PDUs removed from the buffer due to in-order            reception.

Receiving an AMD PDU Outside the Reception Window

If fixed RLC PDU size is configured, then upon reception of an AMD PDUwith SN outside the interval VR(R)≦SN<VR(MR), the receiver shall:

-   -   discard the AMD PDU;    -   if the polling bit in the discarded AMD PDU is set to “1” then    -   initiate the STATUS PDU transfer procedure.

If flexible RLC PDU size is configured, then upon reception of a new AMDPDU whose size added to RxWUTIL exceeds RxWMAX (where RxWMAX<RxWUTIL+newreceived AMD PDU size or RxN) or upon reception of an AMD PDU with SNoutside the interval VR(R)≦SN<VR(MR), the receiver shall:

-   -   discard the AMD PDU;    -   if the polling bit in the discarded AMD PDU is set to “1” then        -   initiate the STATUS PDU transfer procedure.

RLC Status Reporting

RLC status reports containing acknowledgment information to support ARQmay be triggered in various scenarios by the RLC Tx and RLC Rx entities.In order to handle flexible RLC PDU size, the RLC Tx and RLC Rx entitiescan maintain a mapping of RLC PDU SN to the corresponding PDU length inbytes. This allows the calculation and maintenance of the length of theused flow control window in bytes or other byte-based metrics asdescribed above.

An equivalent parameter to Every Poll_PDU PDU, the upper limit for thestate variable VT(PDU) for keeping track of polling, can be configuredin terms of bytes. In this case, the transmitter may have a PDU countpolling mechanism and/or a byte count polling mechanism, such that thetransmitter polls the receiver every Poll_Bytes bytes. For descriptionpurposes, it is assumed herein that the polling parameter provided byhigher layers is called Poll_Bytes. If configured for polling, the RLCtransmitter may trigger a status report by setting the polling bit incertain PDUs as follows:

-   -   The RLC transmitter maintains a counter of the total number of        bytes transmitted in PDUs since the transmission of the last PDU        containing a polling bit, where the last PDU containing a        polling bit can be due to any type of polling trigger, including        for example Poll_PDU, Poll_SDU or Poll_bytes, or alternatively,        may be restricted to the last PDU containing a polling bit        triggered due to the byte polling mechanism.    -   When the counter reaches or exceeds a value Poll_Bytes, the RLC        transmitter sets the polling bit in the PDU (or, alternatively,        the next PDU) that caused the counter to be greater than or        equal to the value Poll_Bytes and resets the counter.

Herein, setting a polling bit refers to a polling request, such that apolling request may consist of POLL SUFI PDU, or it may consist of thesetting of a polling bit in an AMD RLC PDU. The total number of bytestransmitted in PDUs may refer to the size of the PDUs transmitted forthe first time. Alternatively, it can refer to the size of all PDUstransmitted, including retransmissions. The counted total number ofbytes transmitted may only count the first transmission of the RLCacknowledged mode data (AMD) PDU, the RLC AMD PDU segment or a portionof an RLC SDU, where retransmissions of these data portions may not becounted.

Protocol parameters Poll_PDU and Poll_SDU are signaled by upper layers,such as the RRC, to the RLC layer to indicate a PDU count interval. Inaddition, protocol parameter Poll_Bytes in octets can be signaled andconfigured by higher layers. Polling procedures in an RLC transmittermay include the following:

-   -   The RLC transmitter maintains a variable Poll_Octets counter to        keep track of the total number of bytes transmitted in PDUs        since the transmission of the last PDU containing a polling bit,        which may have been triggered due to, for example, the reception        of parameters Poll_PDU, Poll_SDU or Poll_Bytes from higher        layers. Poll_Octets may alternatively keep track of the total        number of bytes transmitted since the last PDU containing a        polling bit triggered due to the byte polling mechanism only.

The Poll_Octets counter may optionally count a total number of bytes ofa first transmission of each RLC acknowledged mode data (AMD) PDU. ThePoll_Octets counter may optionally count only RLC data PDUs, such thatRLC control PDUs are not counted. When the Poll_Octets counter reachesthe Poll_Bytes interval value, the RLC transmitter sets the polling bitin the PDU (or optionally, the next PDU) that makes the Poll_Octetscounter exceed the threshold of Poll_Bytes, and resets the Poll_Octetscounter. The Poll_Octets counter may also be reset if the polling bit isset due to other polling conditions such as the reception of a Poll_PDU.

When flexible RLC PDU sizes are supported for AM RLC, flexible RLC PDUsize mode is set by the RRC layer, and window-based polling isconfigured by upper layers, protocol parameter Poll_Window is signaledby upper layers to the RLC to inform the transmitter to poll thereceiver. Poll_Window can be given in terms of a percentage window or interms of number of bytes. A poll is triggered by the transmitter foreach AMD PDU when the value K is greater than or equal to parameterPoll_Window, where K is the transmission window percentage defined as:K=utilized_window/Maximum_(—) Tx_Window_Size(in octets)  Equation (6)where utilized_window is the length in octets of the window bounded bystate variables VT(A) and VT(S). The utilized_window represents theutilized buffer by the data remaining in the transmission buffer. If thePoll_Window is given in terms of number of bytes, K is equivalent to theutilized_window. Therefore, the transmitter will trigger a pollingrequest if the utilized_window exceeds the number of bytes Poll_windowsignaled by the network.

The RLC transmitter can trigger a status report by setting the pollingbit when the used/utilized Tx window size is above a certain systemconfigured threshold in terms of a number of bytes or a percentage ofthe maximum window size. The RLC receiver can trigger a status reportwhen the used/utilized Rx window size is above a certain systemconfigured threshold in terms of a number of bytes or a percentage ofthe maximum window size. Poll_Window indicates when the transmittershall poll the receiver in the case where “window-based polling” isconfigured by upper layers. A poll is triggered for each AMD PDU when:the value J is greater than parameter Poll_Window, where J is thetransmission window percentage defined as:

$\begin{matrix}{J = {\frac{\left( {4096 + {{VT}(S)} + 1 - {{VT}(A)}} \right){mod}\; 4096}{{VT}({WS})} \times 100}} & {{Equation}\mspace{14mu}(7)}\end{matrix}$where the constant 4096 is the modulus for AM as described in 3GPP TS25.322 V7.1.0 subclause 9.4 and VT(S) is the initial value ofPoll_Window before the AMD PDU is submitted to lower layers.

If flexible RLC PDU size is configured, a poll is also triggered foreach AMD PDU when the value of K is greater than parameter Poll_Window,where K is defined as:

$\begin{matrix}{K = {\frac{{Sum}\mspace{14mu}{of}\mspace{14mu}{RLC}\mspace{11mu}{PDU}\mspace{14mu}{sizes}\mspace{14mu}{from}\mspace{14mu}{{VT}(A)}\mspace{14mu}{to}\mspace{14mu}{{VT}(S)}}{{Maximum}\mspace{14mu}{Transmit}\mspace{14mu}{Window}\mspace{14mu}{Size}} \times 100.}} & {{Equation}\mspace{14mu}(8)}\end{matrix}$

Although the teachings herein are described in the context of RLCtransmission (Tx) and RLC reception (Rx) entities, it is applicable toboth uplink (UE to UTRAN/E-UTRAN) and downlink (UTRAN/E-UTRAN to UE)communications. For example, in the uplink direction, theconfiguration/reconfiguration of the parameter Configured_Tx_Window_Sizecauses:

-   -   The UE to derive the state variable VT(WS) from        Configured_Tx_Window_Size as described above.    -   The UE to update the state variable VT(MS) as described above.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

What is claimed is:
 1. A method for enhancing radio link control (RLC)operations, the method comprising: receiving a control frame indicatinga capacity allocation is a byte allocation; and determining, via aprocessor, a capacity allocation by multiplying a credit by a maximumPDU size, wherein: the capacity allocation=(the credit)×(the maximum PDUsize).
 2. The method of claim 1, wherein the credit is a number of PDUs.3. The method of claim 1, wherein the capacity allocation is calculatedas a number of octets.
 4. The method of claim 1, further comprisingreceiving a frame comprising information specifying a number of bytes ofcredit.
 5. The method of claim 4, further comprising: storing a mappingof a PDU sequence number (SN) to an associated length in bytes; andtransmitting PDUs without exceeding the number of bytes of credit. 6.The method of claim 1, wherein the determining is performed by an RNC.7. The method of claim 6, wherein the RNC is a serving RNC (SRNC). 8.The method of claim 6, wherein the RNC is a controlling RNC (CRNC). 9.The method of claim 1, further comprising determining that flexiblepacket data unit (PDU) size is configured.
 10. A network entitycomprising a memory and a processor, the network entity being configuredat least in part to: receive a control frame indicating a capacityallocation is a byte allocation; and determine a capacity allocation bymultiplying a credit by a maximum PDU size, wherein: the capacityallocation=(the credit)×(the maximum PDU size).
 11. The network entityof claim 10, wherein the credit is a number of PDUs.
 12. The networkentity of claim 10, wherein the capacity allocation is calculated as anumber of octets.
 13. The network entity of claim 10, wherein thenetwork entity is further configured, at least in part, to receive aframe comprising information specifying a number of bytes of credit. 14.The network entity of claim 13, wherein the network entity is furtherconfigured, at least in part, to: store a mapping of a PDU sequencenumber (SN) to an associated length in bytes; and transmit PDUs withoutexceeding the number of bytes of credit.
 15. The network entity of claim10, wherein the network entity is an RNC.
 16. The network entity ofclaim 15, wherein the RNC is a serving RNC (SRNC).
 17. The networkentity of claim 15, wherein the RNC is a controlling RNC (CRNC).
 18. Thenetwork entity of claim 10, wherein the network entity is furtherconfigured, at least in part, to determine that flexible packet dataunit (PDU) size is configured.